PURIFICATION AND PROPERTIES OF THE ECO57I RESTRICTION ENDONUCLEASE AND METHYLASE - PROTOTYPES OF A NEW CLASS (TYPE-IV)
PURIFICATION AND PROPERTIES OF THE ECO57I RESTRICTION ENDONUCLEASE AND METHYLASE - PROTOTYPES OF A NEW CLASS (TYPE-IV)
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DOI：
10.1093/nar/20.22.6043
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发表时间：
1992-11-25
影响因子：
14.9
通讯作者：
BUTKUS, V
中科院分区：
文献类型：
--
作者：
JANULAITIS, A;PETRUSYTE, M;BUTKUS, V
Eco 57 Ⅰ限制性内切酶和甲基化酶从重组质粒上携带Eco 57 Ⅰ基因的大肠杆菌RR 1菌株中纯化至均一。变性甲基化酶的分子量为63 kDa。限制性内切酶以单体形式存在，表观分子量为104-108 kDa。R.Eco57I还具有甲基化酶活性。两种酶的甲基化活性修饰靶序列5 'CTGAAG中的外部A残基，产生N6-甲基腺嘌呤。M.Eco571修饰底物的两条链，而R.Eco571仅修饰一条链。只有甲基化酶被Ca 2+激活。该限制性内切酶显示对Mg 2+的绝对需求，并由Mg 2 + Met刺激。ATP对两种酶的活性均无影响。Eco 57 I酶的亚基结构和酶性质将其与先前描述的所有其他限制性修饰酶区分开来。因此，RM.Eco57I可以被认为是一类新的限制修饰系统的代表，我们建议将其归类为IV型。
The Eco57I restriction endonuclease and methylase were purified to homogeneity from the Ecoli RR1 strain carrying the eco57IRM genes on a recombinant plasmid. The molecular weight of the denaturated methylase is 63 kDa. The restriction endonuclease exists in a monomeric form with an apparent molecular weight of 104-108 kDa. R.Eco57I also possesses methylase activity. The methylation activities of both enzymes modify the outer A residue in the target sequence 5'CTGAAG yielding N6-methyladenine. M.Eco571 modifies both strands of the substrate while R.Eco571 modifies only one. Only the methylase enzyme is stimulated by Ca2+. The restriction endonuclease shows an absolute requirement for Mg2+ and is stimulated by AdoMet. ATP has no influence on either activity of the enzymes. The subunit structure and enzymatic properties of the Eco57I enzymes distinguish them from all other restriction-modification enzymes that have been described previously. Therefore, RM.Eco57I may be regarded as a representative of a novel class of restriction-modification systems, and we propose to classify it as type IV.